Eritrea was a colonial ship of the Italian Regia Marina constructed in the Castellammare Shipyards near Napoli. Construction started in 1935 and she was commissioned in 1937. She served mainly in the Indian and western Pacific Oceans.

The Eritrea (2,170 tons displacement) was constructed for duties as a typical "colonial ship" and was sometimes referred to as a "sloop". She had a novel diesel-electric machinery outfit designed to maximise range.

She was armed with four 120 mm guns, two 40 mm guns, and two 13.2 mm machine guns. The ship also had an extensive engineering workshop on board and could provide repair support to Italian submarines based in East Africa.

A modified sister ship to be called Etiopia was planned, but cancelled on the outbreak of war.

Following Italy's declaration of war on 10 June 1940, colonial ship Eritrea became part of the Italian Royal Navy (Regia Marina). Eritrea was part of the Italian Navy's Red Sea Flotilla located at the port of Massawa in Eritrea.

In February 1941, as the East African Campaign started to go badly for the Italians, Massawa, the home port for Eritrea became more endangered. Along with Ramb I and Ramb II, Eritrea slipped through a British blockade off Perim and sailed into the Indian Ocean on 20 February 1941.

She sailed across the Indian Ocean and ultimately reached Kobe, Japan. Upon reaching Japan, Eritrea was supposed to operate as a commerce raider in the Pacific Ocean. Even though allied with Italy, the authorities of then neutral Japan took a dim view of the idea of an Italian raider operating from neutral Japanese ports. The Japanese refused to comply with the Italian plans and Eritrea was not allowed to leave Kobe.

In December 1941, after the official declaration of war, the Japanese government allowed Eritrea to provide assistance to "transport submarines." These submarines, carrying rare goods, arrived in Japanese-held Penang and Singapore from the distant bases in German-held Bordeaux.